Process for preparing high gloss photographic paper

ABSTRACT

PHOTOGRAPHIC PAPER BASE IS COATED WITH A MIXTURE OF GELATIN, BARIUM SULFATE AND A GELATIN HARDENER, DRIED, COATED WITH AN ALKALINE GELATIN SOLUTION, DRIED, SPRAYED WITH AN ALKALINE FORMALDEHYDE SOLUTION AND DRIED IN CONTACT WITH A HIGHLY POLISHED HEATER METAL DRUM TO OBTAIN A HIGH GLOSS FINISH.

Patented July 11, 1972 PROCESS FOR PREPARING HIGH GLOSS PHOTOGRAPHICPAPER Leonid G. Garth, Rochester, N.Y., assignor to Eastman KodakCompany, Rochester, NY. No Drawing. Filed June 30, 1970, Ser. No. 51,358Int. Cl. B44d 1/44; G03c 1/30 US. Cl. 11764 R 2 Claims ABSTRACT OF THEDISCLOSURE Photographic paper base is coated with a mixture of gelatin,barium sulfate and a gelatin hardener, dried, coated with an alkalinegelatin solution, dried, sprayed with an alkaline formaldehyde solutionand dried in contact with a highly polished heated metal drum to obtaina high gloss finish.

This invention relates to a process for the preparation of aphotographic paper base having a high gloss surface.

It is well known in the art to prepare photographic paper base byapplying a mixture of baryta (barium sulfate), gelatin and gelatinhardening agent such as formaldehyde to a paper surface followed bydrying and calendering the paper to obtain a relatively high glossfinish on the baryta coated surface. A gelatin-silver halide emulsionlayer, or layers, is coated on the surface and photographic prints areprepared by exposing and developing the emulsion layer, washing, drying,etc., as well known in the art. However, the resultant processed paperordinarily must be ferrotyped, i.e. dried in contact with a smoothsurface if the photographic prints are to have a very glossy surface.

I have discovered a process for preparing baryta coated photographicpaper base which provides a permanent glossy surface to the paper anddoes not require the processed paper to be ferrotyped, i.e. the papercan be dried out of contact with a smooth surface and still obtain aglossy surface on the prints.

According to the process of the invention, ordinary photographic paperbase in (a) coated with a gelatinbaryta layer preferably containing agelatin hardener such as formaldehyde and dried. Thereafter, (b) anaqueous alkaline gelatin solution is coated onto the baryta layer anddried after which (c) the resultant gelatin coated surface is treatedwith an alkaline aqueous formaldehyde solution followed by drying thesurface in contact with a smooth heated surface such as a metal drum.The resultant surface is then coated with one or more photographicemulsion layers and after exposure and processing of the element in awell known manner, it is found that the pictures obtained thereon have avery high gloss finish and it is not necessary to ferrotype the surfaceto obtain the desired degree of gloss.

A similar process is described by Swiss Pat. 387,433 wherein apigment-adhesive coated paper is treated with aqueous formaldehydesolution followed by drying the coating in contact with a hot metalsurafce. The patent does not suggest using the above steps (b) and (c)of the present invention which are necessary for production of arelatively permanent glossy surface. In step (b) of the present process,the pH of the alkaline gelatin solution should be about 10.5 to 12.0 forbest results. The gelatin solution is coated so as to obtain about 1 to6 grams gelatin, preferably 2 grams of gelatin per square meter ofcoating surface. In step (c) the formaldehyde solution should have a pHof about 11 to 12.5 or higher, preferably 11.5. A dilute aqueousformaldehyde solution of, for example, 4% formaldehyde can be used forthis purpose. Sufiicient formaldehyde is used to obtain a glossy surfaceand yet not so little that the surface sticks to a heated metal surfacewhen drying at a temperature of about C. for about 10 seconds. Higher orlower drying temperatures can be used With suitable adjustment of dryingtime, i.e. drying longer at lower temperatures.

The following example will serve to illustrate the invention.

EXAMPLE A paper stock comprising aluminum stearate sized paper fiber iscoated with an aqueous mixture of gelatin and baryta containing 1 poundgelatin, 10 pounds barium sulfate, and formaldehyde hardener to obtain20 grams of coating per square meter (dry weight). After drying, asecond coating of an aqueous alkaline gelatin solution pH 10.5 isapplied to the baryta coated paper surface to obtain 2 grams gelatin persquare meter (dry weight) followed by drying. Thereafter, a 4% aqueousformaldehyde solution pH 11.5 is sprayed onto the coated surface whichis then dried for nine seconds in contact with a polished metal drumheated to 190 F. The dried surface having a high gloss is then coatedwith a gelatinsilver halide emulsion layer and dried. The resultantlightsensitive photographic paper is exposed, developed, fixed, Washedand dried with the emulsion surface exposed to the air, i.e. withoutferrotyping. As a result, the surface of the process prints has a veryhigh gloss.

When the same process is carried out in the manner of the Swiss Pat.387,443, but omitting the alkaline gelatin coating step, only a mediumglossy surface is obtained on the prints.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

What I claim is:

1 A process for preparing a photographic paper base having a high glosssurface comprising (a) coating a paper sheet with an aqueous mixture ofbarium sulfate, gelatin and gelatin hardener and drying the coating,

(b) applying to the dried coating an aqueous alkaline gelatin solutionand drying the resultant coating,

(0) treating the resultant coating with an alkaline aqueous solution offormaldehyde,

(d) and drying the resultant coating in contact with a highly polishedheated surface.

2. The process of claim 1 wherein the aqueous gelatin solution has a pHof about 10.5 to 12.0 and is applied so as to obtain about 2 grams ofgelatin per square meter of coating surface and the pH of theformaldehyde solution is about 11.0 to 12.5.

References Cited UNITED STATES PATENTS 2,756,150 7/1956 Griggs et al. W117-34 2,121,205 6/l938 Lippert et al. ll7-34 2,780,560 2/1957 Hanleyll734 2,678,890 5/1954 Leighton 1l764 R 3,288,775 1 H1966 Anderau et a1117-34 FOREIGN PATENTS 387,433 Switzerland lI7-34 1,438,244 France.

WILLIAM D. MARTIN, Primary Examiner W. R. TRENOR, Assistant Examiner US.Cl. X.R.

ll7--34, 81, I56; 96--lll

